Tyrannosaurus rex -- the most fearsome predator ever to have trod the Earth -- had a pint-size precursor, remarkably similar in appearance but no heavier than a human being, according to a new report from a team of scientists. The creature was what Austin Powers might call T. rex's Mini-Me.

The new animal, based on a single fossil smuggled out of China and eventually sold to a private collector, has been named Raptorex -- which means "king raptor." It lived 125 million years ago in a lake-dotted region of northern China.

Raptorex had a huge head, tiny forelimbs and a body built for sprinting, just like T. rex. But this fossil is of a young adult dinosaur, nearly full grown, that was only eight feet from snout to tip of tail, compared with 40 feet for an adult T. rex, according to a paper published Thursday in the online version of the journal Science. It would have weighed only 150 pounds.

This scrambles the picture of mega-predator evolution and raises the question of whether other jumbo dinosaurs had budget-size versions.

The orthodoxy in paleontology has been that T. rex got its peculiar body shape -- the colossal head, powerful jaws and comically short forelimbs, among other features -- as a side effect of evolving into a giant animal. The small arms have been seen as a natural trade-off for the big head. The fossil record shows the limbs becoming shorter as T. rex evolves to monstrous dimensions between about 90 million and 65 million years ago, when it went extinct along with every other species of dinosaur other than birds.

Raptorex, however, shows that having the jaws as the first line of attack rather than the forelimbs worked for bodies at the much smaller scale, and tens of millions of years earlier than T. rex's giant phase. Like T. rex, Raptorex had a bite force so powerful it could chomp through bone.

"What we're looking at is a blueprint for a fast-running set of jaws," University of Chicago paleontologist Paul Sereno, the lead author of the Science paper, said this week. The blueprint works at multiple scales and across tens of millions of years of the Mesozoic era, he added. "This animal really changes the way we look at all tyrannosaur evolution."

"No longer can we describe the big head, the powerful jaw muscles, the tiny forelimbs, the very fleet-footed hind limb, as features of the very large body size and the mega-predatory habits," said study co-author Steve Brusatte, a doctoral candidate at Columbia University and the American Museum of Natural History.

yello-considering how some humans act, having a state practically devoid of them seems an innovation not a fault. Or as we say in the mythical, yet very real, North Dakota-"30 below keeps the riffraff out."

Quite a lot of Wyoming dinosaur finds were from near Medicine Bow, where the bar was named the Diplodocus, or "The Dips" for short. Not far from Laramie. It was a Big Mistake for the Interstate to take a shortcut to bypass Medicine Bow. That stretch gets horrific winter weather; it was known as the Snow Chi Minh Trail.

My qualm after looking at lots and lots of dino bones over the past several weeks is over just how 'authentic' are the displays. Sue the T-Rex stands right at the entrance to to the Field Museum. Then on the balcony overlooking the dinosaur is Sue's 'real' skull with an explanation about how it was too heavy so they used a replica for the main display.

Then in another part of the museum they explained how for Sue they had to fabricate far fewer missing intermediate tail vertebrates than ever before. It told about the artistry of the guy that made up the intervening pieces so that they are indistinguishable from the real thing.

In yet another display case they had a huge pile of more bones from Sue that they knew weren't ribs but they didn't know exactly what they were. The display did say that if they figured out where they went they would add them to Sue eventually. All I know is that when I buy something from Ikea and I have parts left over, I did something wrong.

Finally, in their big impressive display on The History Of Life, they had a little film by the Apatosaurus (nee brontosaurus) about how it had the wrong head on it for dozens of years before the scientists decided that head was too big and belonged to an entirely different type of dinosaur.

Rather than being impressed with the power of evolution, I walked away thinking that these guys just make it up as they go. I was ready to jump on the creationist bandwagon and declare that fossils were buried in the ground six thousand years ago just to confuse us. Because they sure confuse me.

The paper's up at Science Xpress. "Tyrannosaurid Skeletal Design First Evolved at Small Body Size". Mr. Kriegstein, who bought the fossil, is a co-author.

The paper version of Science has a story on revisions to AP science curriculum--a bit of a move away from memorizing facts and toward conceptual understanding. That reminds me of a claim, years ago, that an intro biology course tended to involve learning as many new words as a foreign-language course. Maybe more. At least you wouldn't have to conjugate verbs.

Raptorex sounds like the name of an over-the-counter medicine to me. Something for insomnia or upset stomach from having had too much apatosaurus for example.

A German company presented a new electric car at the Frankfurt show. The E-Tron, or, as translated from French, the T-Urd. It's a concept car, I doubt the name would have survived the marketing department review.

This image is from LOCongress's digital collections. Tis on-kit and visual. Click into this, boys and girls, you must see this:
http://memory.loc.gov/cgi-bin/query/I?ils:8:./temp/~pp_CnQn::displayType=1:m856sd=cph:m856sf=3b48847:@@@mdb=fsaall,brum,detr,swann,look,gottscho,pan,horyd,genthe,var,cai,cd,hh,yan,lomax,ils,prok,brhc,nclc,matpc,iucpub,tgmi,lamb,hec,krb

yellojkt, your logic is in keeping with those in charge of our political discourse, both in Congress and the media. I predict a great future for you should you decide to enter either of these two fields. You could be the next Glen Beck! All you have to do is let that reptilian* portion of of your cranial space go!

I want me one of them Raptorexes. Raptorexi? In fact I want a pair; wouldn't want the one to get lonely, patrolling the yard. I'll settle for one of ScienceTim's large carnivorous birds, but I think a small flock of Raptortures would be excellent at discouraging casual shoppers.

Dang, CqP, yet another major tourist attraction in South Dakota that I just plain missed. I must have been in too big a hurry rushing from that corn palace to the vandalized mountain to stop in Rapid City. Well, next time I'm in the neighborhood.

Would it be to much to assume that this is actually a later version of the "t-Rex" and that like many reptiles that neverstop growing until death, the origional "t-Rex" had more time to grow and in turn grew to a larger scale. of course this sounds obsured because it questions the religiouse faith of evolution, wich says that a bunch of "nothing" created a bit of "everything", and that somehow now "everything" , continues to get bigger, stronger, and smarter. wrong. second law of thermodynamics is just the opposit. But just a thought, didn't mean to rant

Not sure where you're going with them thoughts, soldoutluck. The article notes a couple things: (1) through means that aren't clear (since provenance is not well established), Sereno states that this specimen is several 10's of million years earlier than T. Rex. (2) Skeletal evidence indicates that this animal was nearly as large as it could ever get (if it had lived longer).

yoki, carbon dating is not the trongest point to choose, but it does bring up a good question, how did thy date this Fossil? Carbon is flawed unless it is a controlled environment and we knew the amount of each particle upon it begining, but we don't and the earth is not.

-science tim, i don't believe you understand what i meant, unlike humans where you can tell how large they are going to be reptiles lack the limitations, they don't stop growing, so how could you say that this is as big as it would get?

It's not nothing, soldoutluck. The laws of thermodynamics only apply to closed system-- where there is no energy entering or being removed. We have the sun continually pumping energy into the earth. Just go outside and watch your lawn grow and think about how plants can make "something" from "nothing."

When you think about it, the fact that two cells can unite, and then predictably develop into billions of cells that together form a human being, or millions of cells that form an insect, is itself much more miraclous and hard to believe than evolution itself.

For me, it's far easier to believe that life all has one common origin-- and I mean we have verified this at the genetic and biochemical level, same DNA, and that mistakes and duplications and complex feedback goes on to form new forms of life-- this is really dead easy, we have considerable evidence and are accumulating more.

It's far easier for me to believe this than I can believe that a single fertilized egg, undivided, is a human being already.

It's alive, yeah, but I shed millions of cells everyday that are alive, and those cells aren't human beings in themselves.

Soldoutluck, that is a good point about the growth rate-- but actually while reptiles don't stop growing-- they slow down their growth considerably.

Dinosaurs, I think from the last study I saw, actually grow quickly and then slow down considerably. There's intrabone structure evidence for this.

But I am sure even that is open to interpretion right now and their peers will be demanding proof this is not an immature or dwarfed t-rex (pituitary dwarf?), meaning they would be looking for characteristics that make this clearly a different species.

You obviously remember the debate about the "hobbits" on Flores-- Homo florenesis, and how many people were inclined to believe it was a deformed dwarf, rather than a separate species, until further analysis was done.

This is how science works-- by proposing hypotheses, then challenging them.

In this case, you have proposed a hypothesis-- that this skeleton is a dwarf or immature t-rex-- that actually can be tested, unlike, say, the "creation science" statement that "god made dinosaurs."

And evolution is actually a theory (a larger hypothesis) that has strong evidence to support it. Without it we wouldn't have known to look at the biochemistry of all living things to see the commonalities. Without it, we wouldn't have diabetes using human insulin grown from bioengineered bacteria right now, and before that diabetics were using horse insulin.

How did we guess that horse insulin might work in humans? Again-- evolution.

Evolution is a very useful theory because it has generated many fields of biological research that has been productive.

Oh thank goodness I'm back. My poor computer was sick and had to spend an overnight at the Mac hospital. When I brought her home tonight, she had a small friend with her, a MacBook. This is sort of like getting a new puppy when the old dog starts to stumble, the new one keeps the old one company and smooths the ultimate and inevitable transition. Plus the new one is just so cute!

I'm back from an errand, so I have more time to reply to soldoutluck. I am an astrophysicist, not a paleontologist, so I can only go by what I glean from the article and a lifetime of being an unrepentant dinosaur geek, plus an intensive week of experience this past summer, plus my background in radioactive decay processes. In other words, more paleontologically savvy than your average bear, but way less savvy than most biologists and any professional paleontologist.

Paul Sereno, quoted in the article, cites the fusion of certain bones as indicating that the animal had reached near full growth. Reptiles may continue to grow, but Wilbrod_Gnome has noted that that growth significantly slows past maturity. The present best model (which I am finding increasingly convincing) is that dinosaurs and birds are basically the same kind of critters, differing only in the details of their particular adaptations. Within my limited knowledge, I am not aware of birds having a reputation for life-long growth. My popular-press understanding of dinosaurs suggests that dinosaurs also tend to hit a limit and then stop getting substantially bigger. The average dinosaur lifestyle -- either predator or prey animal -- would not permit an American-style growth process of ever-expanding adiposity.

Dating issues: carbon-dating is ineffective for items more than a few tens of thousands of years old (maybe a hundred thousand years, I suppose). You don't need to know how many carbon atoms were there to begin with. We have good techniques for estimating the ambient carbon isotope distribution in the past, so one only needs to evaluate the ratio of present isotope abundances in order to determine what fraction of carbon-14 has decayed with time to become nitrogen-14. However, you have to have enough carbon-14 left to be able to count, and its half-life is only 5730 years (way, way more than long enough to refute young-Earth Creationists). More than likely, the rough dating for this specimen is from an examination of the rock and association with known deposits in the region from which it is known to have been (illegally) taken. The deposits would be roughly dated according to stratigraphy (layering) and other radioactive-decay dating methods -- this particular layer may not have a radiolytic date, but it probably bears a known relationship to other layers that *are* radiolytically dated. According to Joel's reporting, the specimen was delivered in a block, so there was plenty of rock there -- apparently, enough to associate it with a known unit.

By the way -- before we reach the end of the day, let's not forget the tradition of Global Warming Thursday. Certain things are agreed-upon in the world today, even by conservatives -- at least until they discover that the evidence ineluctably leads them to someplace where they don't want go:

(1) The amount of carbon dioxide in the atmosphere is substantially greater than a hundred years ago. Could it be (some "skeptically" ask) from natural causes?

(2) Carbon dioxide is a greenhouse gas, which causes an atmosphere to retain more heat (Venus, anyone?).

(3) The climate is generally getting warmer.

So, the only remaining question is: is it our fault? This matters since nobody likes to take the blame for something they didn't do, plus it affects the issue of whether we should consider ourselves to be technically capable or empowered to even try to reverse the situation.

The answer is: it is our fault, without a shadow of a doubt. How can we know this? Simple: carbon that is in fossil fuels has no carbon-14 in it, because it was buried many carbon half-lives ago. Fossil fuel carbon also has a dramatically different carbon-13 signature than, say, the heartwood of 100-year old trees or glacial CO2 deposits from the past (C-13 and C-12 (aka, normal isotope) are both stable nuclei). The ambient carbon-14 fraction today is enormously depressed by comparison to the historical and geophysical record. The atmospheric carbon-13 fraction is rapidly changing to become more like the C-13 fraction in fossil fuels. There is no question that modern atmospheric CO2 is becoming dominated by the carbon that was buried in the ground for millions of years and which we dug up/pumped up and burned.

Oops, I almost forgot -- C-14 is depressed with respect to what it *would be*, if it weren't for nuclear weapons, which made a huge increase during the period of above-ground weapons testing. However, that does not account for the change in C-13.

Nicely done Joel. What a lot of intriguing questions this discovery has raised. I like the idea that maybe leading with the teeth had an evolutionary advantage and wasn't just a side effect. I also like the idea that the perceived dominance of big dinosaurs might be wrong. I've always thought there was something very cool about smaller dinosaurs. You know, like Dino.

Reading about Lake Baikal. "U.S. and Russian studies of core sediment in the 1990s provide a detailed record of climatic variation over the past 250,000 years."

Lake bottom sediments change in composition seasonally and provide a record of annual fluctuation much like tree rings. The lake's age is estimated at 25–30 million years, making it one of the most ancient lakes in geological history.

Reeling merrily on topic for a moment, let me suggest the idea - tongue-in-cheek - that 'good design is good design.'

Take, for example, the design of the felis, or, cat. Where prey and resources permot (or evolutionary pressures dictate), that basic design can scale up as large as Siberian Tigers that have been reputed to weigh as much as 800 lb. and be over 10 ft in length, while the smallest cats I'm aware of may as small as 2 or 3 lb. and 20 inches long as adults.

I suppose I could say same for birds, dogs, primates, and other evolutionarily successful basic designs that seem to work well on a variety of scales, evolving to suit a wide range of environmental factors.

Life is anything but boring, especially if we manage to keep evolving (cometary impacts and global warming notwithstanding).

Jumper, I think the Clementine probe back in the 90's showed data indicative of Lunar Polar water ice, too.

In fact, I think that data drove some of the current Orbiter's experiements...

It'd be great if it were true -- one of the largest costs in setting up shop on the moon would be hauling water all the way up there. If there were already water there, that would make things far easier and less expensive. It'd also make the moon a more desirable as a base for missions to other planets -- not only could water be used for sustaining life, but if there were enough of it, it could also be processed for fuel for chemical rockets or used as reaction mass in simple nuclear propulsion systems.

Yes, it's good to have these further indicators of water. I have thought about extracting oxygen from the rocks completely without a supply of H and I don't like the sound of that, you can bet. It's do-able, but that's all I know about it. I've done a lot of high-temp stuff but that's out of my experiences. Ilmanite and lot of electrical current, I guess.

There is so much fine work going on in space these days it's hard to keep track. Very soon we will see this deliberate impact in the lunar crater and subsequently the impact plume analyzed both from inside the plume and remotely. Hawaii will participate.
http://www.nasa.gov/mission_pages/LCROSS/main/LCROSS_crater.html

I checked the paper by Sereno et al (Sereno's email is dinosaur@uchicago.edu, which says something about his life's work).

Although the dinosaur was stolen, the geological provenance of the stone in which it was embedded is clear: "the Lujiatun Beds (Hauterivian-Barremian, ca. 130 Ma) of the Lower Cretaceous Jehol Group in northeast China".

Science also has a neat astronomy news story on Gamma Ray Burst 090423, dated to "a mere 625 million years after the big bang, when the universe was less than 5% of its current age. The photons it spewed into space traveled for more than 13 billion years before reaching Earth."

Howdy boodle,
I've been so swamped in the past month with starting our new life in Chi-town I haven't had much time for boodling (or even lurking), but since I had a few minutes before bed I thought I'd say I miss you guys. I hope I'll be back in the mix soon.

Wilbrod - You ask fine questions, but I think that sometimes you ask too much of folks who are releasing preliminary data.

Just out of curiosity, how are the "scientists" supposed to differentiate between "it was a deformed dwarf [creature x]", and "it was a regular dwarf [creature x]", and "it was a small deformed regular [creature x]", and "it was a small regular [creature x]", a just plain old "small [creature x]", a "regular [creature x]", and a "dwarf [creature x]"?

Time and data will get them there eventually, presumably. But would you require, or even wish, that they withhold all announcements until all possible interpretations of the data have been exhaustively explored? I wouldn't.

Wilbrod - Do not, under any circumstances, read my last comment as an actual criticism. It was a long, fairly obscure joke intended almost entirely to amuse, well, me! It was a riff taken from your remark:
- - -
"The problem with this article is that it's missing diagrams for the door you can open with your forearm.
He is totally missing a chance to boost the door industry, just like Bush boosted the duct tape industry."
- - -

1) The amount of carbon dioxide in the atmosphere is substantially greater than a hundred years ago...

Pish posh, says I. That's just a matter of accounting. The carbon and oxygen have to be somewhere, don't they now? Given all the time & effort we've spent bringing coal & oil to the surface, that's as it should be.

Good morning boodle! Rejoicing in rejoining the living, if only tentatively so.

Back to St. Paul this morning for Mr. F's Army retirement ceremony. Technically he'll still be on active duty for 2 more months, but the new job starts a week from Monday. He's still trying to figure out what to do with his hair. This whole civilian life thing is going to be quite an adventure. Like visiting a foreign country, then realizing you have to stay.

'morning all. the mini-me dino story has gone viral; every single daily has the story. We love our ferocious predator. Speaking of which, in a very rare accident a woman was killed by a black bear North of Montreal. Our black bear are pretty small, 200lbs makes it a good one, it shows you don't need a grizzly-sized animal bear to kill someone.

Those mini-me T-rex at 150lbs must have been the terror of the "early" people pulling chariots with small herbivores.

And it's raining on this day Witch no.2 leaves for France. Darn nice school trip I'd say.

Happy Friday, all! Another busy day here, including the funeral for a WWII vet who was a member of my church. They are dying off fast, our veterans. This gentleman was 85 and had been in poor health for a long time. Although I know she is grieving, his wife said he was ready and she is relieved he is no longer suffering.

Seriously, I think it is extremely exciting that new discoveries are continuing to be made and that our understanding of evolution in general and dinosaurs in particular is continuing to grow in complexity and nuance.

One of the beautiful things about Science is the subtle relationship between theory and observation. No theory is truly complete until there is no more data to examine.

Although I do assert that the "thicker in the middle" proposition is one for the ages.

Confession: I have not yet read this kit or this boodle. Was catching up on previous boo, when I saw jumper's 14 day feat. I am so glad for you, stay positive, stay with the oxygen, stay away from the cancer sticks, my friend.

Now, to read, to dream, to find out what T. rex may have tasted like, hopefully, grilled fresh frogs' legs with some sort of lemon sauce, or a little bernaise.....

'Morning, Boodle. Frosty, tell Mr. F he can start letting his hair grow. And he doesn't have to shine his shoes any more.

How is your health? I don't know what to fax you (besides the all-purpose never-fails chicken soup it couldn't hurt, of course). Aspirin/tylenol/ibuprofen? A gin-and-tonic? Furinol? A nice bagel and lox? What?

You had a dogosaur, Scotty? We were too poor to own a dog pretending to be a dinosaur. We had to use a free-range chicken, pluck all its feathers, and make a big, fierce papier-mache head for it to look like a faux mini-me dogosaur.

Feeling MUCH better today! Slept without incident last night after tons more ginger tea and some crackers, which stayed where they were supposed to. Even had a good breakfast this morning. And, while I don't feel like a million bucks (it would help to *have* a million bucks to see what that feels like), I'm certainly close to it. Yesterday must have been an aberration, as I usually don't get this kind of crud. Okay, then -- I guess I'm good to go for another 20 some-odd years. . . .

Now I gotta get some work done from yesterday. Glad to hear that you're also on the mend, Frosti!

No one has mentioned Barnum Brown and the Hell Creek Formation in southeastern Montana? Other than the fact that Brown worked digging up the Howe Ranch in Shell, Wyoming, Wyoming doesn't have much to do with this story--and, as I mentioned, Brown and Frederick Brewster Loomis were former teammates while working for the AMNH in Colorado, Wyoming and Montana. Brown, who passed at the age of 89 on Feb. 5, 1963, died about 46 years and six months too soo--in my estimation.

So how does a nice opthamologist, Kriegstein, from the Plymouth, Hingham area of Massachusetts, come by such a rare find? Was he just in the Tucson area for winter golf and happened to swing by the show on a whim? That Tucson show fossil show seems to be a hotbed of illicit transactions. I've already mentioned, some months ago, Kirby Seiber's shenanigans there--buying low and selling high.

Perhaps the feds should just post officials from the Immigration and Customs Enforcement there PERMANENTLY. The story below is about vendors affiliated with a rhodochrosite mine in Argentina trying to pull off illicit sales several years ago at that same venue.

Our Alamo City paper is carrying Joel's copy today of this story. I found the AP reporting last night of the same story interesting because in that version, Horner of Montana and the AMNH, says "Not so fast...let's study these bones of the small T. Rex from Mongolia a bit longer before definitive conclusions are drawn." Horner has written a series of books and one of the earlier ones contains a continuation of the Kirby Seiber story and his unusual activities. Some individuals may find the book that was published earlier this year by Kirby, "How to Build a Dinosaur: Extinction Doesn't Have to Last Forever" good reading. Very Jurassic Park.

There is admittedly the science part of this story, but I'm equally if not more interested in the smuggling aspect of the whole affair. Certainly, Kriegstein knows the name of the vendor who came by this fossil in Japan, after it had been smuggled from Mongolia. There must, most certainly, be a record of Kriegstein's transaction in Tucson about a decade ago.

Two hundred pounds would be a full-grown bear in Florida, too. I can't think of anyone having been killed by a bear, here. They are very shy of people, though not necessarily of bee hives.

I recall watching a University of Florida veterinary technician taking organ tissue samples from a freshly-dead bear. I quickly noted that the bear's insides looked, of course, just like illustrations from human anatomy textbooks. A moment of queasiness followed.

ScienceKid#1 asked the same question about an ophthalmologist with a dinosaur fossil. I think it works out pretty straightforwardly:

(1) a potentially costly hobby.
(2) a well-paying day job.

In my own field, amateurs can now afford equipment that would have been enviable for professionals a mere decade ago, and other equipment that is up-to-the-minute: tip-tilt adaptive optics corrects ~70% of seeing problems and is well within the grasp of well-heeled amateur astronomers. Amateurs have much more time to spend on targets, so they become very familiar with them and have lots of opportunities to notice changes. The recent Jupiter impact, for example, was identified by an Australian amateur astronomer.He is submitting a fascinating proposition to the planetary science decadal survey, derived from the experience of this event.

A worrisome element of this dinosaur find is that it rewards a private collector who almost certainly knew that his specimen could not have been obtained by legal means. On the other hand... he really did donate his treasured and expensive possession to science. Tax deductions for donations in kind have a high floor for deductibility, but I don't doubt that this specimen exceeded that floor both in what he paid for it, and what it's actually worth. Even so, he's out a big chunk of change. I like that the coverage on this specimen in Science notes that the naming is not actually for Dr. Kriegstein himself, but for his parents, who are Holocaust survivors.

DotC, black bear attacks are extremely rare. I know of one jogger who got attacked and killed a few years back near Quebec city. She was listening to music while running in the woods, it was a BAD idea and a defensive attack on the part of the bear. The rarest of the rare, a predatory attack, happened maybe 10 years ago in a nearby provincial park. Two tourists were attacked and eaten partially. At the time this was the only predatory attack on record by an Eastern black bear.

Grizzlies are an entirely different story. They like people, for breakfast, lunch or dinner.

200 pounds isn't that large a bear; we regularly had 300 lbs.ers in our yard in Revelstoke.

The worst grizzlie attack I know of was near Pincher Creek several years back. The bear dragged the guy into the woods and covered him with leaves. Snacked on him for days. Took the Parks people weeks to find the remains. They shot the bear.

Our black bears are famously small. Out West in Alberta, Yukon and Alaska they are famously big. And double that for a grizzly.

Yet the small black bear that is pestering us with its raids on bird feeders and gas grills easily bent a 1" steel pipe and a 1 7/8" fence post. The little b@asterd. I've seen it the other morning, it has a tag in its ear, meaning it's been trapped before. That bruin is ripe for the Ursine Relocation program.

I have, from my later science education, a problem with dinosaurs and it is physics. Mass increases as the cube and strength increases as the square. That limits the size of animals. In fact, even a fall as small as 4 feet can injure an African elephant fatally, by breaking a large bone.

So, how did larger animals, like the dinosaurs, overcome this basic physics problem? I have a hard time believing that the gravitational acceleration was different in their time unless the asteroid that wiped them out had unusual mass.

Yeah, but size is an advantage to ruminants because processing cellulose in large batches has an advantage, plus the relative invulnerability of large animals to predation. If we take those advantages to a maximum today, we get African elephants, presumably to the limit of the strength of the bone to hold them up.

What was different 60 mya that allowed larger animals? It is not like early paleontologists were not aware of the problem. They always had the largest dinosaurs pictured half supported in swampy ground but the more modern guys want them trotting around on open plains even to the extent of showing Apatasaurus acting like a giraffe in Jurassic Park and putting all their weight on the hind legs only.